Application of active packaging concepts in the field of food industry
I. Siró, J. Monspartné dr. Sényi
Department of Preservation, Faculty of Food Sciences, Szent István University
J. dr. Kosáry
Department of Applied Chemistry, Faculty of Food Sciences, Szent István University
Introduction
Changes in the way food products are produced, distributed, stored and retailed reflecting the continuing increase in consumer demand for improved quality and extended shelf-life for packaged foods are placing greater and bigger demands on the performance of food packaging. Consumers want to be assured that the packaging is fulfilling its function of protecting the quality, freshness and safety of foods. To provide this assurance and to help improve the performance of the packaging innovative active and intelligent packaging concepts are being developed.
Active packaging is not synonymous with intelligent (or smart) packaging. The two different terms may be defined as follows:
Active packaging: Concepts that change the condition of the packed food to extend shelf-life or to improve safety or sensory properties while maintaining the quality of the food.
Intelligent packaging: Concepts that monitor to give information about the quality of the packed food.
Conditions of the packed food include physiological (e. g. respiration of fruits and vegetables), physical (e. g. desiccation), chemical (e. g. lipid oxidation), infestation (insects) or microbial states (e. g. spoilage bacteria, toxin producing bacteria)
Active packaging includes concepts that will absorb oxygen, ethylene, moisture or remove compounds that may cause taints. Other systems of active packaging release antimicrobial agents, antioxidants, flavours and/or colours. (Rooney, 1995)
In many cases food deterioration is caused by oxidation of food constituents or spoilage by moulds in the presence of O2 therefore the removal and control of oxygen in package headspace and in solutions of food and beverages has been target for the food technologists for a long time. In the last decade the application of vacuum and modified atmosphere packaging appeared successful in extending the shelf-life and quality of the food. However, these technologies do not always remove oxygen completely. Moreover the O2 that penetrates through the packaging film cannot be removed by these technologies. (Vermeiren, 1999)
By use of an O2 scavenger, which absorb the residual oxygen after packaging quality changes of O2-sensitive foods can often minimised.
Active packaging concepts employ a wide range of technologies, each selected to deal with specific problems. In the USA, Japan and Australia, these concepts are being successfully applied to extend shelf-life and the quality of food.
In Europe the development and application of active packaging system have been limited. The main reasons for this are legislative restrictions, a lack of knowledge about their acceptability to consumers, the efficacy of such concepts, and the economic and environmental impact such concepts may have. (Vermuë, 2000) It can be mentioned that the situation in Hungary is worse. The consumers and the producers really do not know what active packaging concepts mean and therefore they are afraid of using it.
From September 2000 the authors investigated some typical Hungarian food products such as sliced bread, sausages and marzipan. The oxygen sensitivity of these products has been documented by this experimental work.
This was just the beginning of a wide range experimental series, which will include even experiments with ethylene absorbers in the packaging of fresh fruit and other active packaging concepts.
Bakery products
Flour and its principle baked product bread are the cheapest and most important staple foods for our nations.
Although many modes of deterioration are possible in bakery products there are three, which are the most important: Mold growth, staling, moisture loss/ gain.
The object in packaging bread is to maintain the bread in a fresh condition by preventing too rapid drying out without providing a too good moisture barrier which would promote mold growth on a soggy crust.
Nowadays, bread is usually packed in an LDPE bag in with the end is twisted and sealed with a strip of adhesive tape. This form of packaging helps retard one mode of deterioration in bread, namely moisture loss.
Some specialty breads such as French may be packaged in LDPE bags perforated with small holes, which allow moisture to escape and thus retain a crisp crust.
There are three approaches to the modified atmosphere packaging of bakery products: Gas packaging, alcohol vapor and oxygen absorbers.
It is very difficult to reduce the oxygen content to a very low level in packages of bakery products. The porous interiors of these products tend to trap oxygen in such a way it does not readily interchange with gas which is flowing through the package as occurs in a simple flushing operation carried out as part of MAP.
Repeated vacuumizing followed by release of vacuum with an anaerobic gas system would probably solve this problem but would also tend to collapse products such as bread and rolls.
One approach to overcome this problem is to place an oxygen absorbent material inside the package after it has been flushed with N2 or CO2.
Sachets containing active agents, which rapidly react with oxygen have been evaluated for this purpose.
In the test reported in 2001, slices of bread “SZEGEDI VÁGOTT” were placed in plastic trays of oxygen impermeable film with an oxygen absorbent sachet (BIOKA) and carefully heat sealed, no mould growth appeared even after prolonged storage at 27 oC.
In further tests in with films (from an Italian firm) with higher oxygen permeability and leaking seals were used, the extensions in mold-free shelf-life were greatly reduced. Permeability of the film was found to be more important than leakage sites in the seals.
It was concluded from these tests that the use of oxygen-absorbing sachets can result in commercially worthwhile increases in shelf life of baked products provided that the packaging material used is sufficiently oxygen impermeable and the package are well sealed.
Fresh meat products (sausages)
The object of the experiment was to compare sausages packaged in different ways. Two types of sausages such as sausages for frying and grilled sausages were investigated. These sausages were packaged in modified atmosphere without BIOKA oxygen scavenger and in modified atmosphere packaging (70% N2, 30% CO2) in combination with BIOKA oxygen scavengers. The samples were stored at 6 oC. During the experiment the microbial quality and the sensorial properties of the samples were followed. The number of several microorganism such as Salmonella spp., S. aureus, E. coli, Enterococcus faecalis, Clostridium perfingens and the total microbial count were measured.
The shelf-life guaranteed by the producer was 21 days and 14 days for grilled sausages and in the case of sausages for frying respectively.
The results showed that both the sausages for frying packaged with and without BIOKA oxygen scavenger in modified atmosphere were acceptable even after 27 days of storage. However in the case of samples packaged without BIOKA oxygen scavenger a moderate sour smell existed after opening the package but it did not cause any problem neither in the microbial quality nor the sensorial properties after frying.
In the case of grilled sausages the samples packaged with BIOKA oxygen scavenger and without BIOKA oxygen scavenger were acceptable even after 37 days of storage. Both the sensorial and the microbial qualities of the samples were good. In both cases the shelf-life of the samples was longer than the guaranteed shelf-life.
Marzipan
Marzipan is one of the most preferred but the most expensive confectionery in Hungary. Marzipan made from ingredients of good quality and using an appropriate manufacturing technology and stored within an adequate circumstance has a relatively long shelf-life. However due to its high lipid and sugar content it is susceptible to rancidation and microbial deterioration. The rancidation is caused by the oxidative changes of the high lipid content exist in the almond which is the main ingredient of marzipan. These oxidative changes mainly involve the lipid-peroxidation of unsaturated fatty acids. The lipid-peroxidation can be catalysed by lipoxigenase enzymes or oxygen.
During the rancidation process in food products arise undesirable compounds of annoying smell and mainly of yellow colour. Moreover these compounds can react with other compounds of food ingredients and secondary alterations take place. (Kosáry et al., 2000)
It is well known from the literature that the kinetics of lipid-peroxidation is effected by the temperature, by the light and by the exposition to the oxygen. Using decreased storing temperature and decreased oxygen content the lipid-peroxidation can be delayed or it can be avoidable. The limitations of the vacuum packaging systems has been already mentioned in the introduction therefore in the case of marzipan modified atmosphere packaging in combination with oxygen scavenger sachets can be an appropriate solution for extending the shelf-life. The oxygen scavengers absorb the residual oxygen after packaging therefore the rancidation of the product can be minimised.
The object of the preliminary studies was to find a method for measuring the lipid-peroxidation of oil content of marzipan products easily and reliable. It was necessary to force the rancidation process and for this purpose the samples were stored in a drying chamber of 55 C. The role of the elevated temperature was to start the lipid-peroxidation as soon as possible. However this method was considered as ineffective because even after 10 weeks of storage the samples did not show any sign of rancidation. This result can be explained by the inadequate amount of oxygen and light. After that another method was used for forcing the rancidation. The samples were stored under infrared light. The temperature at the surface of marzipan samples was the same as used in the first method (55 C). The lipid-peroxidation was characterised by the common used peroxid number. The Figure 1 shows the evolution of peroxid number in the samples stored under infrared light.
Figure 1: Changes in peroxid number (PO) as a function of storage time at 55 °C under infrared light in marzipan samples
However it is important to emphasise that the shelf-life of the products among other conditions such as the quality of the ingredients depends on the way of manufacturing. A part of the manufactured marzipan is handmade while the other part is made by mechanical extrusion. The practical experiences showed that marzipan made by mechanical extrusion are more sensible to oxygen than the others.
In the very near future the authors would like to investigate the role of the manufacturing and the packaging method. Therefore comparisons between marzipan made by hand and by extrusion and stored in air and in modified atmosphere packaging in combination with oxygen scavanger will be made.
It can be concluded that in general the purpose of these experiments and the use of active packaging concepts are to find a balance between a prolonged shelf-life and the food safety.
References:
- J., KOSÁRY, M. TAKÁCS, I. SIRÓ (2000): Study of lipid-peroxidation of oils by intensive peroxidation test IPT. Olaj, Szappan, Kozmetika, 49, 49-53.
- ROONEY, M.L. (ed.) (1995): Active food packaging. Chapman & Hall, London, UK
- VERMEIREN, L., DEVLIEGHERE, F., van BEEST, M., de KRUIJF, N., DEBEVERE, J. (1999): Developments in the active packaging of foods, Trends in F. Sci. & Techn.10, 77-86.
- VERMUË, J. (2000): An overview of active packaging systems in International Conference on Active and Intelligent Packaging, UK.
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